In other words, the kitsch is their equivalent of the fishbowl of cheap pocket multi-tools at every hardware store checkstand, the candy & junk magazines at every grocery store checkstand, and the upbeat “You want fries with that?” query at every fast food checkstand.
Not so surprising after all. That come-on works. It’s almost free money for the retailer. Even as we fall for it we’re gratified by the impulse purchase.
I have a nerdy interest in all things time, and, for that reason, clepsydrae were the first thing that came to my mind too when I read the subject. What I find fascinating about them is that they differed fundamentally from the ancient way of timekeeping. The ancients did not divide the day into 24 hours of equal length; instead, they divided daytime (sunrise to sunset) into twelve day hours, and nighttime (sunset to sunrise) into twelve night hours (a system known as temporal hours). Consequently, day and night hours were of unequal length (except on the equinoxes), and their precise length varied by season. This makes perfect sense if you use sundials for timekeeping, but a clepsydra will count hours of uniform length (though, as you note, with poor accuracy). That’s why the ancients needed to make use of variable scales to convert the time as kept by a clepsydra into their season-dependent temporal hours.
I stumbled across a fascinating water clock (of a sort) in Berlin. The actual timekeeping was done by a pendulum; each swing would release a small amount of water (dyed pale green) into a glass tube. By means of various U bends and siphons, it translated the pendulum swings into the standard 12-hour format. The time could be read by looking at the water level in the tubes.
There’s a similar clock at the children’s museum in Indianapolis.